Yet another half assed answer
Mick, I have had more than my far share of these type of shocks from working in peoples houses. This is normally what I suggest to find the problem.
1. The power company will treat the loss of an earth seriously. If you call them and say the right words (i.e. I think the earth is not connected) they will come out and check. They will only check to the power box but thats a start. (did this on one job cause the earth rod was HOT, ended up this guys earth stake was the only working one for about 8 houses)
2. In most metro areas the neutral and earth are bonded. If this is the way it is your area its worth checking.
3. Could be a single appliance leaking. Most of the time its the defrost heater in the fridge (a classic sign of this is a frdge that sweats or has rusty external surface). Get each device "mega" tested. This checks for insulation between conductors.
4. RCDs and ELCBs are different. RCD will trip if the curent going to and comming from a device is not balanced. ELCBs will trip when they see current on the earth. Also they are often left off circuits that are problematic, easier than fixing the issue. Sad but true...
Yet another unqualified waffle to add to the listhttp://www.woodworkforums.ubeaut.com...ons/icon12.gif